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Bronze

Discrepancy in A-Radio max power among 1242AG, RM-21/22

I have a case open with the TAC, but I was wondering if anyone has seen differing Allowed Power Levels in "sh controller d1" output across different A-Radios (see below). I noticed this when WLSE would only change half my 1242s A radios to assumed max power (15dB/30mW). I started to look at the other A-Radios (RM-21/22) and saw more divergence in Max Power. Some had 17dB/50mW, others 11dB/13mW What's going on?

Two AP1242A radios with different max power levels:

interface Dot11Radio1

Radio AIR-AP1242A, Base Address 0016.9c02.c870, BBlock version 0.00, Software version 5.80.15

Serial number: ALP10064RC1

Number of supported simultaneous BSSID on Dot11Radio1: 8

Carrier Set: Americas (UNI2ML OFDM) (US )

DFS Required: No

Current Frequency: 5180 MHz Channel 36

Allowed Frequencies: 5180(36) 5200(40) 5220(44) 5240(48) 5260(52) 5280(56) 5300(60) 5320(64) 5745(149) 5765(153) 5785(157) 5805(161)

Current Power: 11 dBm

=>Allowed Power Levels: -1 2 5 8 11

interface Dot11Radio1

Radio AIR-AP1242A, Base Address 0016.9c02.a3a0, BBlock version 0.00, Software version 5.80.15

Serial number: ALP10063WK1

Number of supported simultaneous BSSID on Dot11Radio1: 8

Carrier Set: Americas (UNI2ML OFDM) (US )

DFS Required: No

Current Frequency: 5785 MHz Channel 157

Allowed Frequencies: 5180(36) 5200(40) 5220(44) 5240(48) 5260(52) 5280(56) 5300(60) 5320(64) 5745(149) 5765(153) 5785(157) 5805(161)

Current Power: 14 dBm

=>Allowed Power Levels: -1 2 5 8 11 14

Two RM21A radios with different max power levels:

interface Dot11Radio1

Radio AIR-RM21A, Base Address 0012.d98d.8330, BBlock version 0.00, Software version 5.70.5

Serial number: FOC08501GV7

Number of supported simultaneous BSSID on Dot11Radio1: 8

Carrier Set: Americas (UNI2ML OFDM) (US )

DFS Required: No

Current Frequency: 5200 MHz Channel 40

Allowed Frequencies: 5180(36) 5200(40) 5220(44) 5240(48) 5260(52) 5280(56) 5300(60) 5320(64) 5745(149) 5765(153) 5785(157) 5805(161)

Current Power: 15 dBm

=>Allowed Power Levels: -1 2 5 8 11 14 15

interface Dot11Radio1

Radio AIR-RM21A, Address 0012.d98d.8b20, BBlock version 0.00, Software version 5.60.13

Serial number: FOC08501GNP

Carrier Set: Americas (UNI2ML OFDM) (US )

Current Frequency: 5320 MHz Channel 64

Allowed Frequencies: 5180(36) 5200(40) 5220(44) 5240(48) 5260(52) 5280(56) 5300(60) 5320(64) 5745(149) 5765(153) 5785(157) 5805(161)

Current Power: 17 dBm

=>Allowed Power Levels: -1 2 5 8 11 14 15 17

One RM22A radio with 11dB max power level:

interface Dot11Radio1

Radio AIR-RM22A, Base Address 0013.60dc.8710, BBlock version 0.00, Software version 5.70.5

Serial number: FOC090710JU

Number of supported simultaneous BSSID on Dot11Radio1: 8

Carrier Set: Americas (UNI2ML OFDM) (US )

DFS Required: No

Current Frequency: 5200 MHz Channel 40

Allowed Frequencies: 5180(36) 5200(40) 5220(44) 5240(48) 5260(52) 5280(56) 5300(60) 5320(64) 5745(149) 5765(153) 5785(157) 5805(161)

Current Power: 11 dBm

Allowed Power Levels: -1 2 5 8 11

2 REPLIES
Bronze

Re: Discrepancy in A-Radio max power among 1242AG, RM-21/22

I may be answering my own question: could this be due to the different UNI-II channels/bands used (the output showns them to be all UNI2ML however)?

Bronze

Re: Discrepancy in A-Radio max power among 1242AG, RM-21/22

** Answer from TAC Engineer **

Young,

This makes sense. I thought this might be related to the UNI bands somehow. I changed the channels on the 1242s and saw the results you mention below.

So the upshot is:

5 channels @50mW/17dB

1 channel @25mW/14dB

6 channels @13mW/11dB.

There’s more power available in these middle/upper domains than what’s allowed on these radios, even with a 9dBi antenna. Is this because they’re for indoor use?

The FCC has allocated 300 MHz of spectrum for unlicensed operation in the 5 GHz block, 200 MHz of which is at 5.15 MHz to 5.35 MHz, with the other 100 MHz at 5.725 MHz to 5.825 MHz. The spectrum is split into three working "domains." The first 100 MHz in the lower section is restricted to a maximum power output of 50 mW (milliwatts). The second 100 MHz has a more generous 250-mW power budget, while the top 100 MHz is delegated for outdoor applications, with a maximum of 1-watt power output.

This impacts our choice of APs. I was for the 1242AG since it has more memory, newer processor and radios, but we might have to re-think the 1232AG as a better option for RF coverage.

How about making a 1242 with an RM-21 slot? ;)

Thanks Young. Please close this case out. At least I found my first bug.

Regards,

Bruce T. Johnson

--------------------------------------------------------------------------------

From: Young Gil Kim [mailto:kiyoung@cisco.com]

Sent: Thursday, May 04, 2006 4:57 PM

To: Johnson, Bruce T

Subject: 603479117 Discrepancies in A-Radio power on same and different model radios

Hi Bruce,

This is Young Kim from the Cisco TAC regarding case 603479117. There are a few issues for the power discrepancies.

With the RM21A radio:

The RM21A radio antenna is basically two antennas built into one module:

5 dBi omnidirectional and 9 dBi patch antennas (AIR-RM-21A-x-K9)

When in omnidirectional mode you will have all available power settings, but in patch mode you will run into the same restrictions as the RM-22A radio modules.

The available power settings that you can use on the RM-22A and RM-21A in 9 dBi patch mode depends on which radio channel you are using.

For example:

Channel Freq Highest Power

149 5745 17

153 5765 17

157 5785 14

161 5805 11 <= power gets lower the higher in

frequency (closer to the band edge)

In order for the 802.11A radios to pass FCC emissions with the highest

gain antenna that we offer

The device must pass ALL EMISSION TESTING WITH THE HIGHEST GAIN WE

OFFER - when tested using the HIGHEST POWER SETTING available to our

customers.

Therefore, the RM-21 radio (when in LOW gain antenna mode) and since

it's antenna is built in will produce a full 17 dBm across the

entire UNII-3 spectrum.

Since in this mode a user can not connect a higher gain antenna, it

is permitted to run at full power however, when a connectorized model with external RP-TNC antenna ports are used, the power needs to be scaled back on channels 157 and 161 as

these channels are closer to the band edges.

channel 34 - 48 and 161 highest power level is 11

channel 157 highest output is 14

channel 52 - 60, 149 - 153 is 17

There is a documentation bug that has been opened for this lack of information. The bug

ID is CSCeg70287:

show controller dot11 output undocumented

Here is also a useful URL that shows 802.11A transmit power based on band usage:

http://www.vocal.com/data_sheets/802_11a.html

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